PREPARATION

Place noodles in a bowl; add enough warm water to cover and let sit until soft, about 15 minutes. Drain. Combine broth, pepper, garlic, ginger, lemon zest, lime zest, lemon juice and 3 tablespoon fish sauce in a medium saucepan. Season with salt. Bring to a simmer, add noodles and cook 3 minutes more. Using tongs, transfer noodles to a bowl and cover with foil to keep warm. Add mushrooms to broth; season with salt, if desired; simmer 3 minutes more. Add chicken and coconut milk and simmer, stirring, until chicken is just cooked, about 3 minutes. Stir in spinach until it begins to wilt, about 1 minute. Add chopped cilantro and season with remaining 1 tablespoon fish sauce. Using tongs, divide noodles among 4 bowls. Ladle soup into bowls and garnish with sprigs of cilantro and slices of pepper.